B&O 3000, mono sound headphone, no sound over the speakers.

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nongrata Posted: Sun, Apr 12 2015 3:41 PM

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form 1970 (fist model) has a strange problem.

When i listen over the headphone I hear the sound in mono.
If I change the the balance to the right, the sound in the right goes lower and you hear a hum.
To the left the music is loud. 

When I try to listen over the speakers, they do not give any sound.

I tried to measure the 2N3055 but they look ok however they seem to give a different reading because they are still in the circuit.  

Someone has an idea ?

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Dillen replied on Sun, Apr 12 2015 6:11 PM

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Are idle current correct in both channels ?
Swapping left/right inputs to the amplifier will help you find out  if the signal problem is before- or after this stage.

Martin

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nongrata replied on Mon, Apr 13 2015 8:27 AM

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Hi Dillen

Thanks for the suggestions.
Somehow a switch in the back called test was switched on.
Probably turned on by accident when te 3000 was picked up for cleaning.
After switching it back to the normal position the left output made sound on the speaker and headphone.
The right one has no sound but gives a hum.
I took out the two 2N3055 and they seem to be ok.
Hope this evening can check the drivers.